The present disclosure relates generally to a method of servicing a well, and more particularly to the viscosification of a well servicing fluid using polymers comprising betaine units in combination with at least one surfactant.
It is well known in the art that well servicing fluids can be made by batch mixing or on-the-fly mixing processes. Batch mixing processes can be employed when longer mixing times are needed. In “on-the-fly” processes, the well servicing fluid is mixed immediately before, or simultaneously as, the fluid is pumped downhole. For on the fly processes, the mixing generally occurs for a relatively short period of time compared to batch mixing processes.
For an on-the-fly processes to be feasible, the ingredients of the well servicing fluid should be capable of mixing quickly to provide desired well servicing fluid properties. For example, in some instances it may be desirable for the well servicing fluid to reach a target viscosity before being pumped downhole.
In order to achieve desired viscosities, it is well known in the art to employ viscosifying agents. For example, the use of polymers comprising betaine units for viscosifying hydrocarbon well fluids was disclosed by D. V. Satyanarayana Gupta et al., in copending U.S. Patent Application Publication No. 2010/0197530 (“the '530 Application”), published on Aug. 5, 2010, the disclosure of which is hereby incorporated by reference in its entirety. The application discloses a servicing fluid for use in natural gas or oil field wells. The well servicing fluid includes an aqueous brine media and a zwitterionic polymer. The zwitterionic polymer is prepared by polymerization of at least one monomer, Ab, comprising a betaine group and optionally one or more nonionic monomers, Ba.
The zwitterionic polymers of the '530 Application are mixed with brines for a relatively long period of time before a desired viscosity is achieved. For example, the brines are disclosed as being mixed for about 15 minutes at a constant shear at approximately 700 RPMs with a surfactant, such as ammonium salts of polyarylphenyl ether sulfate, until a desired viscosity of the fluid is reached.
It would be desirable to reduce the time it takes to mix well servicing fluid components, such as the zwitterionic polymers of the '530 application. Faster mixing can save time and money. In some instances, it may also provide the ability to mix well servicing fluids on-the-fly. The ability to employ either batch or on-the-fly mixing processes increases process flexibility.
Accordingly, there exists a need for improved well bore-servicing fluids that address one or more of the issues discussed above.